Where did come to us "tailed stars"? Still on the sources of comets are lively discussions, but a single solution has not been developed.

In the XVIII century Herschel, watching nebula, suggested that the comet is a small nebula, moving in interstellar space. In 1796 Laplace in his book "Statement of system of the world" stated the first scientific hypothesis of the origin of comets. Laplace considered them scraps interstellar nebulae, which is incorrect because of differences in the chemical composition of both. However, his suggestion that these objects have interstellar origin, was confirmed by the presence of comets with nearly parabolic orbits. Short-period comets Laplace considered also came from interstellar space, but once captured by the gravity of Jupiter and translated them on short-period orbit. The theory of the Laplace has supporters and at the present time.

In 50-ies of the Dutch astronomer Aoart offered a hypothesis about the existence of comet clouds at a distance of 150 000. that is from the Sun, formed as a result of the explosion of the 10th planet in the Solar system - Phaeton that once existed between Mars and Jupiter. According to academician Century, Fesenkova explosion was the result of too close Phaeton and Jupiter, as in this rapprochement, because of the huge tidal forces, there was a strong internal overheating of the chaise. The force of the explosion was huge. In proof theory can provide a calculation van Flandern, studied the distribution of elements 60 long-period comets and came to the conclusion that 5 million years ago between the orbits of Jupiter and Mars exploded planet weight in 90 of the earth's mass (comparable on weight with Saturn). As a result of the explosion of a large part of the substance in the form of a comet nucleus fragments of ice crust), asteroids and meteorites has left the Solar system, part stayed in the periphery as the Oort cloud, part of the substance remained at the same orbit Phaeton, where it circulates in the form of asteroids, cometary nuclei and meteorites.

Some of the comet's nucleus preserved relic ice under the loose refractory insulating layer components, and still in the asteroid belt sometimes reveal short-period comets moving in nearly circular orbits. An example of such a comet can be a comet Smirnova - Black, opened in 1975.

Currently accepted hypothesis gravitational condensation of all bodies of the Solar system from primary gas-dust cloud that had similar with sun chemical composition. In the cold area of the clouds condensed giant planets: Jupiter, Saturn, Uranus, Neptune. They have absorbed the most abundant elements of the protoplanetary cloud, resulting in their weight has increased so much that they began to capture not only the solids, and gases. In the same cold zone was formed and ice cores of comets, which are partly went to the formation of giant planets, but partly, as the growth of the masses of the planets were dropped them on the periphery of the Solar system, where he formed a "reservoir" comets - the Oort cloud.

A study of the elements nearly parabolic cometary orbits, as well as the use of methods of celestial mechanics, it was proved that the Oort cloud really exists and is quite stable: its half-life is about one billion years. This cloud is constantly updated from various sources, so it does not cease to exist.

F. Wipl believes in the Solar system besides the Oort cloud exists and is closer to the area, densely populated with comets. It is located beyond the orbit of Neptune that contains about 10 comets and it is the visible perturbations of Neptune, which previously was attributed to Pluto, as it has a lot on two orders of magnitude greater than the mass of Pluto. This belt could be caused by so-called "diffusion cometary orbits", theory which was most fully developed Riga astronomer K. Stancom. It is a very slow accumulation of small planetary perturbations, which becomes a gradual reduction of the semimajor axis of the elliptical orbit of the comet.

Thus, for millions of years, many comets that previously belonged to the Oort cloud, change their orbits so that their perihelion (closest distance from the Sun) begin to concentrate near the farthest planet from the Sun giant Neptune, with a large mass and extended in scope. Therefore, it is possible existence is predicted by Iplom comet belt beyond Neptune.

In the further evolution of comet orbits of the belt wipe proceeds much more rapidly, depending on the rapprochement with Neptune. When there is a strong convergence transformation orbit: Neptune its magnetic field has the effect that after the release of its application, the comet starts moving sharply hyperbolic orbit that leads either to her ejection from the Solar system, or it continues to move inside planetary systems, where it can again be exposed to the giant planets, or will move to the Sun on sustainable elliptical orbit, its aphelion (the point of greatest distance from the Sun) by showing belonging to the family of Neptune.

According to I. E. Kazimirchak-Polonskaya, diffusion leads to the accumulation circular cometary orbits between Uranus and Neptune, Saturn and Uranus, Jupiter and Saturn, which are also sources cometary nuclei.

A number of difficulties that occurred in the hypothesis capture, especially in times of Laplace, in the explanation of the origin of comets, has prompted scientists to look for other sources of comets. So, for example, the French scientist Lagrange, based on the absence of sharp initial hyperbole, there is only direct movements in the system of short-period comets in the family of Jupiter, has stated a hypothesis about the eruption, that is volcanic, the origin of comets from different planets. Lagrange supported Proctor, who explained the existence of comets in the Solar system strongest volcanic activity on Jupiter. But in order to fragment the surface of Jupiter could overcome the gravitational field of the planet, he would need to inform the initial speed of 60 km/S. the Emergence of such speeds during volcanic eruptions is unrealistic, so the hypothesis eruptive origin of comets is physically untenable. But in our time, it supports a number of scientists, developing additions and corrections to it.

There are other hypotheses about the origin of comets that have not received such wide distribution, as the hypothesis of interstellar origin of comets, Oort cloud and eruptive education comets.